The present invention generally relates to methods and systems of operating a host bus and, more particularly, to methods and systems for varying bus frequencies and parameters.
A bus provides for signal communications between electronic devices. In a computer system, the central processing unit and the chipset are connected via a host bus, such as Front Side Bus (FSB) or Hyper Transport (HT). Hyper Transport improves the communication link or links between interconnected processors, supporting chips, and/or I/O devices and provides high speed, high performance, and/or point-to-point links in networking, communications, and other embedded applications. The possible advantages of a flexible, extensible, and/or simple bus structure make it a broadly adopted design today.
Personal computers are constantly evolving to provide users with higher performance at lower cost. However, power consumption usually is balanced against performance and demands of various applications. For example, for portable systems such as laptop computers and personal digital assistants (PDAs), power consumption may be a variable factor. When there are more processing tasks or needs for a higher processing speed, a bus-operating frequency may be increased at the cost of more power consumption. Concurrently, bus chains coupled between interconnected processors and devices may also be operated at a higher frequency. For example, the frequency of the bus connecting the processor and memories may be increased when a higher speed of reading/writing data from/to memory is needed.
Because the host bus frequency may be varied to save power or to increase performance, parameters corresponding to the bus frequency, such as the I/O drive strength, bus timing, and loading on bus, should be updated with such a change of the bus frequency. The bus frequency of the host bus and the corresponding parameters may be changed by the following operation. First, parameters corresponding to the current frequency are updated to new parameters associated with a new frequency. Next, a link connected to the host bus at the current frequency is disabled. The link is then reconnected at the new frequency to operate the host bus at the new frequency with the new parameters. FIG. 1 illustrates a conventional solution, including the above steps for changing the bus frequency.
However, this approach may cause the bus to operate at an old frequency while using parameters corresponding to a new frequency before disabling the link. For example, the host bridge operation may fail if it operates at the old frequency with new parameters.